Magneto breaker contact point opening and closing indicator



l939- M. L. JOHNSON ET AL 2,184,304

I MAGNETO BREAKER CONTACT POINT OPENING AND CLOSING INDICATOR Original Filed Dec. 20, 1935 "2 SheetsSheet 1 Mei v.24; AEE Joan/s a J H J. Aosg- D 1939- 'M. L. JOHNSON ET AL 2,184,304 I MAGNETO BREAKER CONTACT POINT OPENING AND CLOSING INDICATOR Original Fiied Dec. 20, 1935 2 Sheets-Sheet 2 imm do H/V ROSE I/JTTOR/VEYS MENSAL LEE Janus/so I Patented Dec. 26,1939

UNITED STATES PATENT oFFlca;

monsro innaxan CONTACT romr oramo AND cnosmo mnrcn'ron MensalLee Johnson, Kalamazoo, Mich, and John 3. Rose, Dayton, Ohio Application December 20, 1935, Serial No. 55,486

Renewed September 12, 1939 6 Claims. (on. raw-311) (oi-antes use the act or March a, 1883, as

amendcdApril. 39, 1928; 370 G. 757) The invention described herein may be manufactured and used by orfor the Government formeter were connected in series with the two contact points of the breaker mechanism. The l rotor' of the magneto was then slowly turned by hand, the ofi" and on flashing oi the lamp or indication of the meter determined the exact moment or instant of the opening or closing of the aforementioned contact points.

Physical breaking of any portion of the circuit interconnecting the breaker mechanism with the primary coil of a magneto oflers two serious drawbacks. Additidnal housing room must be provided for initial wire severance or terminaldisconnection. Then, upon completion of breaker mechanism adjustment, the severed wire or the disconnected terminal must be resoldered. It is a primary object of our invention to completely eliminate the necessity of performing either of the above steps.

In an electrical system comprising a testing circuit plus a magneto primary and breaker points in parallel, said system further incorporatingas a part of the complete circuit two parallel paths, one of which is of high reactance and low resistance (namely, the magneto primary) and the other of which is of low reactance and low resistance (namely, the breaker points) both of which, either in parallel or singly, have-a resistance very low compared to the rest of the circuit (1. e., the test circuit), it is extremely difficult to determine when the low reactance, low resistance path (1. e., the breaker points) is opened and closed when continuous current isused. This is due to the fact that the reactive characteristics of the parallel paths have no .effeet on the flow of continuous current- If, however, a changing current,'such as alternating currentor interrupted direct current, is applied to the test circuit incorporating these parallel.

paths, the reactive characteristics of the parallel paths will have a very decided and usable effect on the flow of current. When the low reactance path is open. all current in the test circuit will have to flow through the high rcactance path which, if 'its'reactance is of a magnitude compoints; and

parable with the impedance of the rest of the test circuit, will play an important part in. determining the magnitude of the current. Now,

. if the low reactance, low resistance path is closed,

it has for all the practical purposes of our in-= vention, the effect of short circuiting the high reactance path of the circuit, because it ofiers very little opposition to the flow of the alternating current. This very materially changes the impedance of the entire test circuit, with a consequent material change of current, which change when proper measuring means are employed scrvesto indicate when the low ,reactance, low

resistance path is open or closed without the necessity of disconnecting the high reactance,

low resistance path from the-circuit.

This invention further provides an instru- -ment by means of which indications may be obtained at a place .or position magneto.

It is a still further object of our invention to provide an indicator that is inexpensive, compact and readily portable. While capable of positive and exact indication, it requires no line mechanical adjustment.

With the foregoing advantages and other .obiectsin view, which will appear as the description proceeds, the invention consists or certain new and novel features and combinations which will be hereinafter more fully illustrated and described in the accompanying drawings and more particularly pointed out in the appended claims,

Referring to the drawings, in which nr'als remote from the of like character designate similar parts through= out the several es:

Fig. 1 shows an existingmethcd of detecting opening and closing of magneto breaker points;

Fig. 2 shows one of our methods of detecting opening and closing of'magneto' breaker points;

Fig. 3 shows substitution of a telephone re- 40 indicator," including electric lamps, in Fig.2:

Fig. 6' shows substitution of a low wattage electric lamp ndicator in Fig. 2;

Fig. '7 hows another of our methods of detecting opening and closing of magneto breaker Fig. 8 shows our invention in the form ot a portable instrument.

. Fig. 1 illustrates diagrammatically an electrical system widely employed tor determining the moment or instant at which the breaker points oi a magneto circuit open or close. The system may be said to/comprise a testing circuit composed of a battery ii, an ammeter 22 and a switch 29 connected in series with terminals and 8; a magneto primary composed of a primary coil 21; and breaker points composedor a breaker 25 and a condenser 28; the said magneto primary and breaker points being connected in parallel with terminals 23 and 24. The system is complete upon final interconnection of terminal 8 with terminal 23 and terminal! with terminal With commencement of actual test, one of the lead wires or the primary coil 21 is severed at X, thus completely breaking its interconnection with the aforesaid testing circuit. The switch 29 is then closed and the rotor of the magneto slowly turned by hand. The exact moment or instant of the opening or closing of the contact points of the breaker is indicated by a sudden OH or on indication change in the ammeter 22. It is at once obvious that the ammeter 22 may be replaced with an electric lamp without in any wise altering the nature of 26 the test conducted. Upon test completion, the terminals 8 and 9 are disconnected from the terminals 23 and 24, following which the severance at X" is eliminated by resoldering severed wire ends or severed wire end and mating terminal.

Our invention discloses two methods of parts disposition, both involving a source of alternating voltage, a changing impedance to be measured and a device for indicating impedance 86 change, whereby the testing difficulties enumerated above may be completely eliminated.

In Fig. 2, a Wheatstones bridge circuit i is' composed of equal resistors 2 having a common output terminal 2 and 01' equal condensers 4 10 having a common output terminal 5. The open ends of the left-hand resistor 2 and condenser 4 are joined by an input terminal 6, while similar ends or the right-hand resistor 2 and condenser 4 are Joined by an input terminal 1. The circult of the right-hand condenser 4 is broken, terminals 8 and a being provided for the open ends thereof. Current from a battery I0 is supplied to a high frequency interrupter II (1000 cycles) and from thence to terminals 6 and 1 of the bridge circuit. One pole of the battery I0 is Joined with terminal I2 (01' field i2) 0! the interrupter ii, while the remaining pole thereof is joined in common with terminal 2 oi the bridge circuit l and terminal l4 (of breaker ll) of the interrupter II. The remaining terminal i0 01 the field i3 is joined incommon with the remaining terminal l1 of the breaker l5 and terminal 1 of the bridge circuit I. -It will be noted that the output terminals 2 and 5 of the bridge circuit i are joined respectively to terminals l2 and I! or an indicator 20o, composed of an instrument rectifier 2| and an ammeter 22, such that for a balanced condition of the bridge circult I,no current from the interrupter will fiow through the indicator 22a. Qn the other hand, due to interconnection of terminals 2 and I with terminals 22 and 24 o! a breaker 25, an unbalanced condition of the bridge circuit l 70 will obtain whenever the contact points of the breaker 25 are in the "open" position shown in Fig. 1 and alternating current from the interrupter II will flow through the indicator 204. It will also be noted that a condenser 20 is connected across the terminals 22 and 24 o! the magneto primary coil 21, terminals 22 and 24 being common to both breaker and coil.

In operation, the bridge circuit i, the battery iii, the high frequency interrupter II, and the indicators 200. 20c, 20d or 20c are encased within 5 and the indicator 20b detachably carried by a housing. Flexible conductors are provided for the terminals 8 and 9. whereby the same may be readily secured to terminals 23 and 24 of a breaker and coil assembly awaiting adjustment. 10 With the aforesaid conductors properly installed, the slightest opening of breaker points removes the short circuit of the breaker 25 across the terminals 8 and 2, shunting the inductance of the primary coil 21 there-across. Introduction 15 of the latter inductance in the upper right-hand arm of the bridge circuit I throws the bridge completely out of balance and current from the interrupter Ii will flow through the indicators 200. through 20c. Actuation oi the indicators W 200 through 20c shows the exact instant or moment of breaker point' opening or closing.

In Fig. 3, the indicator 20a composed of the instrument rectifier 2| and the ammeter 22 of Figure 2 is replaced by an indicator 20b, made up 25 of a telephone receiver 33 operably connected to the terminals i8 and IQ of the aforesaid Fig. 1.

In Fig. 4, the indicator 20a of Fig. 2 is replaced by an indicator 20c composed of a voltmeter 34 operatively connected to the terminals i8 and I9 30 of the said Fig. 2. The instrument rectifier 2| of Fig. 2 is retained inFig. 5 and forms part of the indicator 20d. The open tips of the rectifier 2i are operably connected to the two lead wires of a sensitive relay 35. An 35 interrupter circuit 36, of therelay 35, is composed of a battery 31 having one pole connected to the interrupter 38 of the relay 35 and the other pole jointly connected to an open circuited lamp 39 and a switch 40, the remaining pole of the switch 40 40 being connected to a closed circuited lamp 4|.

In Fig. 6, the indicator 20a of Fig. 2 is replaced by an indicator 20c composed of a low wattage lamp 42 operatively connected to the terminals l8 and IQ of the aforementioned Fig. 2. 5

It is obvious from the above descriptions of Figs. 2 through 6, that, a telephone receiver, an

alternating current voltmeter or an electric lamp may be severally substituted for the instrument rectifier 2i and the ammeter 22 shown in Fig, 2, as may equally well be substituted a sensitive relay tor the ammeter 22 0! Fig. 2 without departing from the scope of our invention. Similarly, any convenient source of alternating current, including the commercial sixty-cycle supply, may be substituted for the interrupted current supply furnished by the battery l0 and the interrupter I i of Figs. 2 and 7.

' A second embodiment of our invention is shown in Fig. 'l, in which the battery ill, the high fre- 00 quency interrupter II, the indicator 20a, the magneto breaker 25 and the primary coil 21 of Fig. 1 have been retained, unaltered. It should be noted, however, that one extremity of a condenser 4a, a resistor 22, and a condenser 411 have common connection with terminal ll of the indicator 20a and terminal 22 or the magneto breaker 2I'and primary coil 21. The remaining extremities of the condenser 4a and resistor 22,

as well as terminal i2 01 the interrupter II, have common connection with terminal is or the indicator 20a "and terminal 24 01' the magneto breaker 28 and primary coil 21. 'The remaining Q extremity o! the condenser 41: is connected .to terminalll'o! the'interrupter l|.. Terminal l2 This alternating E. M. F. is impressed through the condenser 4b across the terminals of the condenser do, the resistor 28, the indicator 20a and the terminals 23 and 24 of the magneto under test. It should be especially noted that'all of the aforesaid units are in shunt with one an-' other. Whenever the contact points of the breaker 25 are in closed position, the alternating E. M. F. across the aforementioned units will be practically-zero and no deflection of the indicator 20a; will result. On the other hand, whenever the contact points of the breaker 25 are in the open position shown in Fig. 6, the

short circuit across the magneto terminals 23 and 24 will be removed and the-reactances 21 (magneto primary coil) and 26 (magneto condenser) will be placed in shunt withthe indicator 20a,

the condenser la, the resistor 28 and the E. M. F. source. The indicator 20:; will thereupon indicate the amount of voltage generated across its terminals. This voltage and the resulting amount of indicator deflection will depend on the amount of impedance produced by the magneto primary coil 27 and the magneto condenser 26, as well as that produced by the condenser dot and resistor 28. It should be noted that the value of the impedance due to the condenser to and the resistor 28 would normally be adjusted to give near full scale deflection of ammeter 22 when the external reactance (magneto) is great.

Fig. 8 shows our invention in the form of a portable instrument, adapted to encase the parts arrangements of Figs. 2 and 7 within a housing 30. For access to "the interior, the housing 30 is provided with a hinged lid 3!. The dial face of the ammeter 22 is positioned flush with the top surface of the lid 3i. Flexible conductors 32 are provided for instrument interconnection with the magneto under observation. By simple substitution of the telephone receiver 33 or the lamps 3S and M or the lamp 42 for theamrneter 22 of Figs. 2 and 7, the parts arrangements of Fig. 3 or Fig. 5 or Fig. 6 can similarly be encased within the housing 30 of'Fig. 8.

We claim:

1. A test circuit for use in' connection with amagneto primary-coil of high reactance and low resistance connected inv parallel with a breaker device of low reactance and low resistance comprising, coupling means adapted tobe connected across both said primary coil and breaker device, means for supplying an alternating current to said circuit for obtaining a high impedance change in said primary coil when said breaker device is opened or closed and means for indicating such change.

2. A test circuit for use'in connection with a magneto primary coil of high reactance and low resistance connected in parallel with a breaker device of low reactance and low resistance comprising, a Wheatstone bridge with-one of its arms including said parallelly connected primary coil and breaker device and having means across its output to indicate impedance change and a source of alternating current connected to the input of said bridge circuit.

3. A portable .testing device for use with a magneto circuit having a primary winding of. high reactance and low resistance and amake and break means of low reactance and low resistance shunted across said primary winding comprising, a source of alternating current supply, a pair of flexible conductors adapted for connecting said source of supply to said winding primary and said make and break means in parallel relation and means for indicating impedance change by the change in the current flow when said make and break means is opened or closed.

-4. In a testing apparatus for determining the instant of make andbreak of an impedance device having a high reactance. and low resistance connected in parallel with a make and break device having a low reactance and low resistance, means adapted to be connected across both said impedance device and'said make and break de? vice for obtaining a balanced condition and an out of balance condition when said make and break device is .closed and opened, including an alternating current source of supply.

5. In a testing apparatus for determining the instant of make and .break of an impedance device having a high reactance and low resistance connected in parallel with a make and break device having a low. reactance and low resistance,

and havinga low reactance and low resistance and means for supplying an alternating current to said circuit.

MENSALLIEE JOHNSON.

JOHN J. ROSE. 

